Kenneth Hester most likely died alone at the bottom of a stairwell on Chicago's West Side.

On Sept. 30, two days before his 26th birthday, detectives found Hester's body in an East Garfield Park neighborhood apartment building after he overdosed on heroin mixed with fentanyl, a potent painkiller typically prescribed for cancer patients.

Through September, Hester is one of 40 people in Cook County who pathologists have confirmed died from using fentanyl, the county medical examiner's office announced Monday. The toxicology reports reveal a sharp rise in the number of fentanyl-related fatalities in Cook County, as investigators recorded 19 accidental deaths involving fentanyl last year and 14 in 2013.

However, the number could be higher. Investigators in the medical examiner's office only began routine testing for fentanyl in June. Prior to that, testing for fentanyl was left to the discretion of the pathologist. Also, 74 people overdosed in a 72-hour period ending Oct. 1, a weekend that may not be fully accounted for in this year's partial tally.

Hester gave in to peer pressure and got hooked on drugs about three years ago, said his mother, Jacque Young. Despite several attempts to get clean, Hester's life had been in a tailspin ever since, she said.

"He's really been trying to kick it," Young said in an interview shortly after his death. "He really didn't want to do it anymore. These people kept calling him."

Nearly a decade since the onset of a drug epidemic that claimed nearly 1,000 lives nationwide, illicitly produced fentanyl has re-emerged in the United States, causing more than 700 deaths from late 2013 to early 2015, according to the U.S. Drug Enforcement Administration.

The October overdoses in Chicago prompted police to hone in on two alleged gang members, Mario Wofford, 26, and Alfonzo Sylvester, 24. The men, reputed members of the Unknown Vice Lords, were accused of selling $720 worth of heroin to undercover Chicago police officers that month in the 3900 block of West Congress Parkway, court records show.

While authorities initially thought the drug was fentanyl-laced heroin, lab results revealed it was actually fentanyl cut with an over-the-counter sleep medication. Wofford and Sylvester were arraigned on multiple drug charges, including manufacturing and delivery of fentanyl, in October. They are scheduled to return to court Jan. 14.

No additional charges had been filed as of Monday, according to state's attorney spokeswoman Tandra Simonton.

Drug dealers are cutting heroin with fentanyl to make a more potent product. The powerful, euphoria-inducing narcotic is 30 to 50 times more potent than heroin and significantly increases the risk of overdose deaths.

Dealers, however, continue to consciously market the dangerous mix, and users continue to seek it out. Dealers have set up shop on Chicago's West Side along Interstate 290, which has garnered the nickname Heroin Highway because the dealers also serve a significant population of drug users in the suburbs.

"For the public's safety, we try to get it off the street as soon as possible," said Chicago police Capt. Daniel O'Shea, who heads the Westside Narcotics Initiative. "It pops up every now and then, and most people would think drug users would stay away, but they are drawn to it like flies to a light."

Greg Scott, director of research at Chicago Recovery Alliance, a nonprofit that gives away supplies like clean syringes to prevent the spread of diseases, said some users try to avoid fentanyl.

"In my experience, people don't like the effects of fentanyl because it's too profound, it's too pronounced, it's very difficult to calculate a dose," Scott said. "It can act like as a paralytic. The reports from people who overdosed say that unlike heroin, where you sort of drift out into a sleep, fentanyl turns you to stone. You're cognizant of the overdose being imminent."

While the number of drug overdoses dropped after Wofford and Sylvester's arrests, authorities said fentanyl is still being sold on the streets, often marketed by drug dealers with distinct colored baggies.

Dealers generally make their products identifiable to create customer loyalty or to serve as a warning, according to Dan Bigg, director of Chicago Recovery Alliance.

But the marketing ploys aren't limited to Chicago, which has served as a heroin pipeline to other Midwestern states.

Authorities traced fentanyl-laced heroin recovered during a June bust in Marion, Ohio, to Chicago, according to published reports. The sapphire drugs were believed to have been colored with fabric dye and sold under the street name "blue drop." The reports said blue drop, which has been linked to Chicago, was blamed for 30 overdoses and two deaths earlier this year in Marion.

In Milwaukee, a needle exchange program posted signs, cautioning users of dangerous drugs coming from Chicago after the October overdoses, according to Bigg.

"Heroin, like any other commodity, comes through Chicago," Bigg said.

Mexican drug cartels have had a monopoly on most of the drugs on Chicago's streets, according to Special Agent in Charge Dennis Wichern, who heads the DEA Chicago Division. The city's heroin still largely comes from across the country's southern border, as it did in the mid-2000s. Fentanyl was also produced in clandestine labs in Mexico until authorities dismantled those operations in 2006.

Young, Hester's mother, said her son went from smoking marijuana at the end of high school to using heroin. At first, he was snorting the drug, Young said. But then he was injecting it.

Hester's drug use was especially uncomfortable for Young because she has a younger son and didn't want Hester to keep his drugs at her home.

"He lied to me all the time," Young said. "He never told the truth about drug use."

Hester spent time in prison for aggravated robbery and had also been locked up for drug possession, DuPage County court records show. But his mother said there was a period where "he'd been doing really good," doing heating and air conditioning repair work, and drywall.

"He was trying to survive and be sober," Young said.

But the heroin proved too much to overcome for Hester, who had been in and out of rehab several times in the months before his death, according to his mother. She described him as a good kid who loved to fish.

"He was a follower, and that was his problem," Young said. "Anything anybody was doing, he was right there with them."